Radar device

A radar device transmits an electric wave whose band is spread by a PN code, receives a reflected wave of the electric wave from an object 10, detects correlation between a received signal and a PN code which is delayed, and thereby detects the object. A receiving part 18 connects three receiving antennas 16a.about.16c sequentially one by one, thereby to receive a reflected wave from an object. The three receiving antennas are arranged having their directions so staggered that their antenna beam patterns partly overlap with each other. A correlation detection circuit 19 detects such a slide width that a value of correlation between a received signal received by each of the antennas and the PN code exceeds a predetermined threshold. An operation part 12 obtains an azimuth of an object based on the detected slide width and beam pattern characteristics of the antennas.

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Claims

1. A radar device which transmits an electric wave, receives a reflected wave of said electric wave from an object, and thereby detects said object, said radar device comprising:

a plurality of antennas each having an antenna beam pattern having a predetermined directivity, said antennas being arranged such that the antenna beam patterns of said antennas are adjacent to each other, and the antenna beam patterns are partly overlapping with each other,
frequency measurement means for measuring a frequency of how often said object is detected by each of said antennas, and
azimuth measurement means for obtaining an azimuth of said detected object, based on (i) said measured frequency for each of said antennas and (ii) beam pattern characteristics of each of said antennas.

2. A radar device according to claim 1, wherein said azimuth measurement means calculates a detection probability of said object based on said measured frequency, obtains in advance a relation between detection probability and azimuth based on said beam pattern characteristics of said antennas, and obtains an azimuth of said object based on said calculated detection probability and said relation between detection probability and azimuth.

3. A radar device which transmits an electric wave, receives a reflected wave of said electric wave from an object, and thereby detects said object, said radar device comprising:

a plurality of antennas each having an antenna beam pattern having a predetermined directivity, said antennas being arranged such that the antenna beam patterns of said antennas are adjacent to each other, and the antenna beam patterns are partly overlapping with each other,
frequency measurement means for measuring a frequency of how often said object is detected by each of said antennas,
signal strength measurement means for measuring a strength of a received signal from said object, received by each of said antennas, and
azimuth measurement means for obtaining an azimuth of said detected object, based on (i) said measured frequency for each of said antennas, (ii) said measured signal strength and (iii) beam pattern characteristics of each of said antennas.

4. A radar device according to claim 3, wherein said azimuth measurement means calculates a detection probability based on said measured frequency, calculates a probability strength ratio of beams based on said calculated detection probability and said measured signal strength, obtains in advance a relation between signal strength ratio and azimuth based on beam pattern characteristics of said antennas, and obtains an azimuth of said object based on said calculated probability signal strength ratio and said relation between the signal strength ratio and azimuth.

5. A radar device according to claim 3, wherein said radar device further comprises tracking means for tracking an object, said plurality of antennas comprise at least three antennas, and said azimuth measurement means stores in, advance a conversion function for obtaining a corresponding azimuth from a signal strength ratio of adjacent beams, calculates a detection probability based on said measured frequency, obtains a probability signal strength based on said calculated detection probability and said measured signal strength, compares values of probability signal strength of the respective beams with each other, thereby to judge whether said object is detected by a side lobe of each beam or detected by a main lobe of each beam or detected due to false tracking by said tracking means, calculates a probability signal strength ratio of beams based on such values of probability signal strength of received signals that are judged to be detected by main lobes of beams, and obtains an azimuth of said object utilizing said stored conversion function based on said calculated probability signal strength ratio.

6. A radar device according to claim 5, said azimuth measurement means judges whether said object is detected by a side lobe of each beam or detected by a main lobe of each beam or detected due to false tracking by said tracking means, by judging whether values of probability signal strength of received signals by adjacent beams show a physical contradiction of measurement which can not occur in measurement by a main lobe, and when a value of probability signal strength shows a contradiction, said azimuth measurement means judges that said value is detected by a side lobe and eliminates said value from calculation for obtaining said probability signal strength ratio, and when values of probability signal strength do not show a contradiction, said azimuth measurement means judges whether values of strength of said received signals are saturated or not, and eliminates a value of probability strength of a received signal whose value of strength is not judged to be saturated, from calculation for obtaining said probability signal strength ratio.

7. A radar device according to claim 6, wherein said azimuth measurement means judges that there is a physical contradiction of measurement, when both beams which are adjacent to a reference beam on both sides show a value of probability signal strength greater than the value of probability signal strength of said reference beam.

8. A radar device according to claim 3, wherein said radar device transmits an electric wave whose band is spread by a PN code, receives a reflected wave of said electric wave from an object, detects a correlation between a received signal and said PN code which is delayed, and thereby detects said object, said signal strength measurement means detects such a range of delay time of said PN code that a detected value of said correlation exceeds a predetermined threshold, and said azimuth measurement means calculates a detection probability based on said measured frequency, calculates a probability signal strength ratio of beams based on said calculated detection probability and said measured signal strength, obtains in advance a relation between signal strength ratio and azimuth based on beam pattern characteristics of said antennas, and obtains an azimuth of said object based on said calculated probability signal strength ratio and said relation between signal strength ratio and azimuth.

9. A radar device according to claim 3, wherein said radar device transmits an electric wave whose band is spread by a PN code, receives a reflected wave of said electric wave from an object, detects a correlation between a received signal and said PN code which is delayed, and thereby detects said object, and said signal strength measurement means detects such a range of delay time of said PN code that a value of said detected correlation exceeds a predetermined threshold.

10. A radar device which transmits an electric wave, receives a reflected wave of said electric wave from an object, and thereby detects said object, said radar device comprising:

a plurality of antennas each having an antenna beam pattern having a predetermined directivity, said antennas being arranged such that the antenna beam patterns of said antennas are adjacent to each other, and the antenna beam patterns are partly overlapping with each other,
frequency measurement means for measuring a frequency of how often said object is detected by each of said antennas,
signal strength measurement means for measuring a strength of a received signal from said object, received by each of said antennas, and
azimuth measurement means for obtaining an azimuth of said detected object, based on (i) said measured frequency for each of said antennas, (ii) said measured signal strength and (iii) beam pattern characteristics of each of said antennas, and
tracking means for tracking an object,
wherein said plurality of antennas comprise at least three antennas, and
said azimuth measurement means stores in advance a conversion function for obtaining a corresponding azimuth from a signal strength ratio of adjacent beams, compares measured values of signal strength of the respective beams with each other, thereby to judge whether said object is detected by a side lobe of each beam or detected by a main lobe of each beam or detected due to false tracking by said tracking means, calculates a signal strength ratio of beams based on such values of strength of received signals that are judged to be detected by main lobes of beams, and obtains an azimuth of said object utilizing said stored conversion function based on said calculated signal strength ratio.

11. A radar device according to claim 10, wherein:

said azimuth measurement means judges whether said object is detected by a side lobe of each beam or detected by a main lobe of each beam or detected due to false tracking by said tracking means, by judging whether values of strength of received signals of adjacent beams show a physical contradiction of measurement which can not occur in measurement by a main lobe, and when a value of signal strength shows a contradiction,
said azimuth measurement means judges that said value is detected by a side lobe and eliminates said value from calculation for obtaining said signal strength ratio, and when values of signal strength do not show a contradiction, and
said azimuth measurement means judges whether values of strength of said received signals are saturated or not, and eliminates a value of strength of a received signal which is not judged to be saturated, from a calculation for obtaining said signal strength ratio.

12. A radar device according to claim 11, wherein said azimuth measurement means judges that there is a physical contradiction of measurement, when both beams which are adjacent to a reference beam on both sides show a value of signal strength greater than the value of signal strength of said reference beam.

Referenced Cited
U.S. Patent Documents
4219812 August 26, 1980 Rittenbach
5731781 March 24, 1998 Reed
Foreign Patent Documents
3-160384 July 1991 JPX
3-206988 September 1991 JPX
5-87914 April 1993 JPX
6-242230 September 1994 JPX
7-271514 October 1995 JPX
8-278362 October 1996 JPX
8-327731 December 1996 JPX
Patent History
Patent number: 5959571
Type: Grant
Filed: Dec 11, 1997
Date of Patent: Sep 28, 1999
Assignee: The Furukawa Electric Co., Ltd. (Tokyo)
Inventors: Yasushi Aoyagi (Yokohama), Toshihide Fukuchi (Hiratsuka), Kiyoshi Inoue (Atsugi), Ryuji Kohno (Yokohama)
Primary Examiner: John B. Sotomayor
Law Firm: Frishauf, Holtz, Goodman, Langer & Chick, P.C.
Application Number: 8/981,054
Classifications
Current U.S. Class: Radar Mounted On And Controls Land Vehicle (342/70); With Correlation (342/145); Combined With Determining Direction (342/146)
International Classification: G01S 1393;